The disclosed embodiments relate to a medical device. Specifically, the disclosed embodiments relate to a catheter and balloon catheter used for diagnosing or treating a stenosis site or an obstructed segment formed inside a blood vessel or digestive organ.
A stenosis site or an obstructed segment formed in a blood vessel, bile duct, pancreatic duct, or the like may restrict the flow of blood, bile (gall), pancreatic fluid or the like, respectively. Catheters are widely used for diagnosing or treating such a stenosis site or an obstructed segment.
In general, a catheter includes a tubular inner layer, an outer layer covering the outer periphery of the inner layer, and a reinforcement layer arranged between the inner layer and the outer layer. In such a catheter where the inner layer is joined with the outer layer through the reinforcement layer, it is difficult to improve the joining strength between the inner layer and the outer layer.
As one known way of improving the joining strength between the inner layer and the outer layer, a protruding portion may be provided in the inner layer, the protruding portion protruding to the outer layer side through a gap in the reinforcement layer and extending in the axial direction so as to enter into the outer layer (see WO 2015/012185).
However, in the catheter described in WO 2015/012185, the protruding portion of the inner layer only extends in one direction from the proximal end to the distal end. Therefore, disadvantageously, the outer layer may be susceptible to detaching from the inner layer when the outer layer is dragged in the distal direction by a stenosis site or an obstructed segment. Further, the protruding portion of the inner layer is only provided on the outside of the reinforcement layer. Stress may therefore be concentrated at the joining region between the protruding portion of the inner layer and the outer layer due to bending of the catheter when the catheter is inserted through a curved blood vessel, bile duct, pancreatic duct, or the like. Therefore, the problem remains that the outer layer may be susceptible to detaching from the inner layer.